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Emma Marris

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The ladder-shaped figure on this cave wall in Spain dates back at least 65,000 years.Credit: P. Saura

Neanderthals painted caves in what is now Spain before their cousins, Homo sapiens, even arrived in Europe, according to research published today in Science1. The finding suggests that the extinct hominids, once assumed to be intellectually inferior to humans, may have been artists with complex beliefs.

Ladder-like shapes, dots and handprints were painted and stenciled deep in caves at three sites in Spain. Their precise meaning may forever be unknowable, says Alistair Pike, an archaeologist at the University of Southampton, UK, who co-authored the study, but they were almost certainly meaningful to our lost kin. “It wasn’t simply decorating your living space,” Pike says. “People were making journeys into the darkness.”

Humans are thought to have arrived in Europe from Africa around 40,000–45,000 years ago. The three caves in different parts of Spain yielded artworks that are at least 65,000 years old, according to uranium-thorium dating of calcium carbonate that had formed on top of the art.

These mineral deposits develop slowly, as water containing calcium comes into contact with cave surfaces. The water also contains trace levels of uranium from the rock. After the calcium carbonate has precipitated out of the water, a clock of sorts begins to tick, as uranium decays into thorium at a steady, known rate.

Uranium-thorium dating has been used in geology for decades, but has seldom been employed to estimate the age of cave art. Some archaeologists are sceptical of the approach. They suggest that the calcium carbonate could have dissolved and re-crystallized after it was first formed — a process that could have also washed away some uranium, making a sample of the mineral appear older than it is.

Anticipating objections about its dating method, Pike’s team collected samples from the outer, middle and inner layers of the calcium carbonate crust and dated them separately. As they expected, the inner samples closest to the art yielded the oldest dates, and the outer samples had younger dates because they would have been later layers of precipitate. “We can’t think of any processes that would re-crystalize the calcite and still keep them in stratigraphic order,” Pike says. The researchers waited three years to publish their results after finding their first clearly pre-human date so they could collect multiple examples and publish their methodology.

Some archaeologists, however, remain unconvinced. “In my opinion, we have to be cautious with these ‘quite old’ results until we have a much larger corpus of dating results,” says Roberto Ontañón Peredo, an archaeologist at the Prehistory and Archaeology Museum of Cantabria in Santander, Spain. “We have to keep a cool head.”

Pike suggests that such reluctance to believe that Neanderthals were creating cave art may have less to do with methodological disputes than plain old species-ism. “People are very prejudiced against Neanderthals,” he says.

Paola Villa, an archaeologist who studies Neanderthal culture at the University of Colorado Boulder, says that Neanderthals have an undeserved reputation as moronic brutes. She says that since their bodies were “archaic” in the sense of having features of older hominids — such as heavier bones and pronounced brow ridges — everyone assumed they were “behaviourally archaic” as well. “They were stereotyped as knuckle-dragging dimwits,” she says.

This assumption has fed into theories about their extinction, which have tended to hinge on humans outcompeting slower, dumber Neanderthals. But Villa says a careful review of the research shows “no support for a cognitive gap between Neanderthals and modern humans”. Newer theories instead focus on factors such as low population density and “assimilation by interbreeding” with humans.

The ladder-like art Pike and his colleagues ascribe to Neanderthal artists has, inside its rectangular forms, faint paintings of animals. These remain a mystery, but Pike speculates that they might be the result of “modern humans coming in and adding their own art”. Humans and Neanderthals may have thought alike, interbred and even — in a way — collaborated artistically, he says.